Transposition-Based Plant Transformation

Agrobacterium T-DNAs were used to deliver transposable Dissociation (Ds) elements into the nuclei of potato (Solanum tuberosum) cells. A double-selection system was applied to enrich for plants that only contained a transposed Ds element. This system consisted of a positive selection for the neomycin phosphotransferase (nptII) gene positioned within Ds followed by a negative selection against stable integration of the cytosine deaminase (codA) gene-containing T-DNA. Sixteen of 29 transgenic plants were found to contain a transposed element while lacking any superfluous T-DNA sequences. The occurrence of this genotype indicates that Ds elements can transpose from relatively short extrachromosomal DNA molecules into the plant genome. The frequency of single-copy Ds transformation was determined at 0.3%, which is only about 2.5-fold lower than the potato transformation frequency for backbone-free and single-copy T-DNAs. Because of the generally high expression levels of genes positioned within transposed elements, the new transformation method may find broad applicability to crops that are accessible to Agrobacterium T-DNA transfer.